Water tank



FIG. 1 is a front perspective view of a water tank showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof;

FIG. 7 is a bottom plan view thereof; and,

FIG. 8 is a front perspective view, shown with the toilet bowl engaged.

The dotted line showing of the toilet bowl is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a water tank, as shown and described. 